NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part2/13696

Text File | 1996-08-05 | 1.9 KB | 72 lines

Path: kuhub.cc.ukans.edu!anh
From: [e-mail] (TRAN PHAN ANH)
Newsgroups: comp.lang.c
Subject: Re: reversing a string
Message-ID: <[e-mail]>
Date: 9 Apr 96 14:40:11 CDT
References: <4k6cjl$[e-mail]> <4kb1s7$[e-mail]> <[e-mail]>
Organization: University of Kansas Academic Computing Services

Something like this?  Or is the s2 argument considered an extra variable.

Anh


#include <stdio.h>
#include <string.h>

void reverse(char *s1, char *s2)
{
  if(s1>=s2)
    return;

  *s1^=*s2;
  *s2^=*s1;
  *s1^=*s2;

  reverse(s1+1,s2-1);
}


int main(int argc, char *argv[])
{
  printf("Arg: %s\n",argv[1]);

  reverse(argv[1],&argv[1][strlen(argv[1])-1]);

  printf("Result: %s\n",argv[1]);
}





In article <[e-mail]>, Lawrence Kirby <[e-mail]> writes:
> In article <4kb1s7$[e-mail]>
>            [e-mail] "John Murphy" writes:
>
>>In article <4k6cjl$[e-mail]>, [e-mail]
>>says...
>>>
>>>I have a challenge from a friend of mine.  He wanted me to reverse a string
>>>with recursion without using any additional variables or loops.  I got mine
>>>to work by using exclusive or, but I needed an additional variable.  Can
>>>someone help with this problem without using the additional variable?
>>>
>>>Thanks
>>You can swap two variables, x and y, with the following series of exclusive
>>or's:
>>        x ^= y;
>>        y ^= x;
>>        x ^= y;
>
> From what he wrote I believe Leland was already doing that. The problem is
> to write the entire function without using an additional variable. It
> can be done! :-)
>
> --
> -----------------------------------------
> Lawrence Kirby | [e-mail]
> Wilts, England | [e-mail]
> -----------------------------------------